Generally, in a field requiring information security, there is employed an authentication technique using mutually shared confidential information and encoding as means for certifying transmission and reception of confidential information and self validity.
An application range of the authentication technique is very wide, and when this technique is applied to a storage device, this technique is used for protecting user's data and protecting a copyright of contents in some cases. As application examples for protecting a copyright of contents, there are known certification of validity of an SD card (registered trademark) as secure storage and CPRM (Content Protection for Recordable Media) for playing back, recording and managing secret information for protecting contents.